Electric discharge device



'May 17, 1932.

w. F. HENDRY 1,858,737

ELECTRIC DISCHARGE DEVICE Filed April 4. 1927 2 Sheets-Sheet l May 17, 1932. w. F. HENDRY ELECTRIC DISCHARGE DEYVICE Filed April 4, 1927 2 Sheets-Sheet 2 n -illlllzilllill ...Il QB Patented May 17, 1932 UNITED STATES PATENT oEFlcE WILLIAM r. Hmmm?, or ossnvnm. NEW Yonx, Assrexvon. EY misma Assia To MANHATTAN mmarcAL SUPPLY conrm, nrc.. or um: cn'Y, m

msm', Al conroaA'rroN or NEW unam' ELEUIBIC DIBGEABGE DEVICE Application med April 4, 1927. Serial lo. 180,788.

This invention relates to new and useful improvements in electric discharge devices, and particularly to rare gas-filled devices which, owing to the electrical discharge taking place, are rendered luminous and may be used as illuminators, signs, or the like.

Various type of devices of this character are known in the art and may in general be divided into two classes: discharge tubesin which the electrodes are provided inside of the envelope, and tubes-in which the electrodes are outside of the envelope. In discharge tubes of the former type, it has been customary to provide internal electrodes hav` ing large active areas, since it was thought that otherwise the life of the device would be too short.

It is the object of the present invention to provide a rare gas :filled discharge tube with internal electrodes so proportioned and designed that the tube operates for a long period of time without noticeable gas absorption. I have found that with electrodes constructed in accordance with the present invention, good results are obtained with electrodes having an active area of 1.5 square decimeters per ampcres or less.

I have found that luminescent tubes provided with electrodes of substantially the same construction as is described in my Patent No. 1,628,045, and lled with a rare gas or a mixture of gases, will operate for a long period of time without the tendency to deteriorate. A small area of the electrode is active, the body of the electrode as well as its lead-in wire being protected by a spaced insulation against bombardment by positive particles.

I have found that while such spaced insulation a'ords good protection with pressures up to about 2,500 v., if higher potentials are applied, part ofthe discharge will go around the protecting insulation and attack the leadin wire or its glass or quartz cover, below the insulation. vWith the electrodes spaced farther apart than is necessary Where the device is used as a current rectifier, the heavy positive particles may acquire great velocity and may on this account also cause damage. In order to prevent this, in accordance with the present invention, I provide a barrier in the form of glass, mica, or other suitable material, which blocks the passage of sitlve particles towards the lead-in wire. 's barrier will mechanically retard the advance of the positive particles. Furthermore, a positive charge will collect on such barrier which will also act to repel positive particles havlng a tendency to travel towards the lead- 1n wire. If necessary, more than one barrier may be provided for this purpose.

Discharge tubes equipped with my improved electrodes may be operated as as metric devices where luminescencev is e ected by the positive column. In this case the electrode is so mounted that a mere point thereof is rendered active. When operated as a symmetric device, a larger area (still less than 1.5 square decimeters per ampere) of each electrode is exposed. B an asymmetric device I mean a device in w ch the current flow for a given voltage is greater when one electrode is the anode than when it is the cathode.

Heretofore, unless certain precautions were observed great diiiiculty was encountered in operating a discharge tube of the luminescent type at current densities exceeding one ampere per 1.5 square decimeters of active elec'- trode surface. I have found that by properly shaping the working area of the electrode, and b decreasing its heat insulatin properties, t at such a tube may be operate at a relatively higher current density than has heretofore been thoughtpractical, with' out causing disintegration of the electrode lead-in wires, and hardening of the gas content.

The invention with itsA further objects and advantages will be more clearly understood by reference to the following description and accompanying drawings of a preferred embodiment thereof.

In the drawings, Fig. 1 represents an asymmetric tube constructed in accordance with my invention.

Fig. 2 is a cross sectional view of electrode 2 of Fig. 1. 4

Fig. 3 is a cross section of a modification of the electrode shown in Fig. 2.

trode structure disclosed in Fig.- 4. h h

In Fig. 1, reference numeral 1 indicates an envelope of glass or other transparent or translucent material having in one end thereof an electrode 2 and in the other end thereof an electrode3. y

In Fig. 2, reference numeral 1 indicates the envelope of a tube having an inwardly turned end portion 15. Portion 15 has a perforated extension 1() within which is placed an aluminum rod 8 to which is attached a carbon button comprising base ortion 6 and a point 3. The lead-in wire 9 is attached to the 'end of rod 8 and extends to the outside ofthe glass envelope. Surrounding the extension 10 and supporting the base por tion 6 is a sleeve of insulating material,v7. The sleeve 7' has a shoulder 12 which rests upon the end of extension 10 and serves to prevent relative displacement of the button and portion 15. Surrounding the sleeve 7 and button isla cylinder 5 of insulating material. The cylinder has a perforation 11 which registers with the outside .of sleeve 7. In the end of cylinder 5 is provided a small perforation 4 through which the point 3, of the button, extends. The point 3 fits closely within the perforation 4 but does not touch the walls thereof.

'The cylinder 5 has at its other end ashoulder 18 to which is secured a ferrule 16. The ferrule V16 is attached to portion 15 by means of -a shoulder 17. Surrounding the cylinder 5 is an insulating barrier 13 which at one end engagesferrule 16. 1

The other end of barrier 13 is flared out and engages a deformed portion 14 of envelope 1, which serves to prevent longitudinal displacement of the barrier relative to the cylinder 5.

Fig. 3 shows an electrode substantially similar to that shown in Fig. 2 except that no barrie-r is provided. In this figure the cylinder 5 has two annular members 19 and 20 attached to the base thereof, which register with corresponding annular members 21 and 22 which are attached to the end of envelope 1. In this figure, the entire electrode assembly is held together by ferrule 16 which engages shoulder 18 of cylinder 1 and shoulder 17 of annular member 22.

In Fig. 4, the electrode 3 is larger than in asymmetric tubes. Its diameter is about 1l inch and de nding on the current to be carried, it projects about l, 1,4 or 1/8 inch beyond the insulating sleeve 5, or is flushed therewith. The separation between insulation 5 and carbon 3 is about twenty-thousandths of an inch. The carbon cylinder 3 is seated on. a projection 25 of the sleeve. Otherwise, the construction is like the one shown in Fig. 2. Instead of or in addition to the glass barrier, 13, the space between the insulation 5 and the glass vessel 1 may be filled with glass wool or other suitable material as indicated at26.V Of course, inv this structure both electrodes ofthe tube will be identical. 1

' Fig. 5 showsa tube wherein the active electrode surface is less than 1.5 square decimeters per ampere of current flowing through the tube.l It has been known that when the ordinary luminescent discharge tube employing a filling of neon or other inert gas is operated at a current density in excess of one ampere per 1.5 square'decimeters of active electrode surface that so-called sputtering occurs, resulting in particles of the metal electrode being given off at relatively high velocities and at relatively high temperatures.

These particles if not impeded reach the walls of the tube Where they combine with or mechanically embrace atoms of the gas-filling, with a consequent hardening of the tube. The construction and proportions of the electrode shown in Fig. 5 are such as to materially reduce sputtering and hardening. For this purpose the electrode consists of a solid metal rod of aluminum or carbon or their equivalents. Near the right hand end of the electrode is an annular ridge 28 which registers with a corresponding annular depression on the interior of the cylindrical insulating tube 5. The tube 5 is also providedat its right hand end on its exterior with the flange 29. The lead-in conductor 9 is fastened to the left hand end of the electrode 3 `in any suitable manner. It will be noted that the right hand end of the electrode is spaced very slightly from the surrounding tube 5 similarly to the construction shown in Figs. 2, 3 and 4. The extreme right hand end of the electrode instead of being a ilat surface-is reentrant and forms a hollow cylindrical surface. The entire cavity between the electrode structure and the envelope to the left of flange 29 is packed with glass wool. This packing serves the dual'purpose of preventinv' ionization in the space around the electrodae and lead-in wire and also acting as a conductor or dissipator of heat from the solid electrode to the glass envelope. In addition, this packing serves to hold the entire electrode assembly from relative movement with respect to the ticles will reach the surface of the envelope.

vIf desired, in order to reduce the chances of these sputtered particles leaving the end of the electrode, this electrode may be made in the form of a hollow sphere having a small orice, it being understood that the exterior4 surface of this sphere is insulated similarly to the insulation of the cylindrical end of electrode 3.

Preferably neon or other rare gas or gases are used and the usual precautions are observed in the filling and curing of the tube.

1. In a luminescent tube, an envelope filledwith a rare gas, two widely spaced electrodes within said envelope, at. least one of sald electrodes having its active surface in the form of a hollow cylinder, said cylinder being surrounded by a sleeve of insulatin material spaced from the exterior surface o said hollow cylinder a slight distance, and heat conducting means filling the spacebetween the nonactive 'portion ofA said electrode and said envelope for reducing the operating temperature of the electrodes. A

2. In a luminescent tube, an envelope filled with a rare gas, two'widely spaced electrodes within said envelope, a heat conducting filling for conducting heat from one of said electrodes to said envelope said filling surrounding the major portion of said electrode and being positioned directly between' the said electrode and the walls of the envelope.

3. In a luminescent tube, a rod-like aluminum electrode having one end thereof hollow, insulation surrounding said hollow end but spaced apart therefrom, a distance but slightly greater than the distance through which an electron must fall to produce ionization at the impressed potential and means for dissipating the heat generated in said electrode, said means comprising a body of heat conducting material disposed radially beween said electrode and the Walls of said tu e. 4. In a luminescent discharge tube, an envelope having a filling of gas at reduced pressure, a pair of widely spaced electrodes within said envelope, one of said electrodes having a cavity in the end thereof, means for confining the discharge to said cavity and means for conducting heat from the electrode to the walls of the envelope, said means comprising a acking of heat conducting, electrically insu ating material placed between the electrode and walls of the tube, said packing serving as a barrier to the passage of undesired dscharge.

5. In an electrical discharge device, an

y envelope.

envelope containin a filling of gas at reduced pressure, a pairo widely s aced electrodes ywithin said envelope, one o said electrodes .having a cavity in the end thereof, means for confining the discharge to said cavit and means extending between the electro e and the wall of the envelope for preventing disf charge from passing .to the base of the electrode.

6. In an electrical discharge device, an envelope containing a filling of gas at reduced pressure, a pair of widely spaced electrodesV within said envelope, a sleeve of insulatin material surroundingv each electrode an spaced therefrom a slight distance, and a flange of insulating material extending from said sleeve'to the surrounding wall of the 7. A device in accordance with claim 6 wherein a packing of lheat conducting material is placed between the electrode strllcf ture and the wall of the envelope, 'back of the flange.y

8. v In a luminescent tube, an'envelope containing a rare gas, two widely.spaced electrodes within said envelope, one of-said electrodes being formed as a hollow cylinder at its inner end and having its active surface restricted to the annular end. and interior of said cylinder, and heat-conducting means filling the space between the non-active portion of said electrode and said envelope.

9. In a luminescent discharge tube, an envelope having a filling of gas at reduced pressure, a pair of widely s acedelectrodes within said envelope, one o said electrodes being surrounded by a sleeve`of insulating material spaced but a slight distance therefrom a flange of insulating material-,extending be tween the said sleeve and the wall of the envelope, and a packing of insulating material disposed between the electrode and the wall of the envelope, back of the flange.

In testimony whereof, I have signed my name to `this specification this 1st day of lll 

